Critical to the application of these exciting technologies within child psychiatry are ethical considerations. Ethics is central to all research, but special issues arise when dealing with subjects who are particularly vulnerable by virtue of their age and dependence, as well as by virtue of impairments resulting from psychiatric disorders. In this section, Arnold and colleagues outline the guiding ethical principles in research with children and address the challenges specific to functional neuroimaging studies of both normal control children and those with psychiatric disorders. Specific risks imposed by functional neuroimaging and informed consent/assent issues are examined, and methods for minimizing such risks are described.